Machine elements of this kind can be used for many different applications. If the machine element is used as a locking device, friction-locking shaft/hub connections can be achieved due to the ring component design with adjusting device. In applications such as this, care is taken that the geometry of the individual ring-shaped components forms a symmetrical unit that is as close as possible to perfect. When the ring components are axially compressed by the adjusting device, a uniform transverse contraction in the direction of shaft and hub results. This contraction permits achieving a centering effect that is rated at the level of the hydro-expansion principle. To enable a high level of force transmission via the adjusting device, steel materials are essentially used for the individual ring components.
A further application as machine element concerns guide sleeves that serve as circular, linear guide elements in the manufacture of machines and jigs. The application of such guide sleeves is appropriate in instances where the advantages of a slideway, for example a high degree of absorption, are to be utilized and where at the same time a minimal amount of guide play is specified. Guide sleeves are therefore used particularly on guide racks, on circular carriage guides as well as on tailstock center sleeves. In addition to the discussed linear movement, simultaneous rotating movements are also possible. However, for lubricating reasons, a rotating movement cannot be achieved only in the sense of a friction-type bearing. To adjust an optimal joint clearance for every operating situation on the guide sleeves, soft materials may be used such as, for example, bronze materials.
Since hydraulically lubricated, adjustable multi-lobe radial friction bearings, which are mainly used in machine design, also have ring components that may be tensioned with respect to each other by an adjusting device, the basic solutions developed for locking devices and guide sleeves can also be transferred to such radial friction bearing applications.
However, particularly preferred in this instance are adjusting nut solutions or ring nuts, which may be specified with extreme accuracy and uniform locking forces in relation to their thread flanks for spindle threads and such like as third components.
One representative of such an adjusting nut as a machine element is described in DE 25 44 498 C3. This known solution describes a ring nut in the sense of an adjusting nut. Although formed as a single piece, the adjusting nut is subdivided into ring components by a first annular groove that originates from the external circumference surface and a second annular groove that is offset from the first annular groove and extends from the internal circumference surface. One of the ring components serves as a counter-ring, between which is disposed a substantially smaller intermediate ring that bridges the annular grooves. The intermediate ring is connected with its inner circumference to one of the rings and with its external circumference to the other one of these rings. The counter-ring and the intermediate ring have a common thread at their connection point. The ring nut may be locked by several, individually adjustable screws that extend parallel to the axis of the ring nut. The screws are disposed evenly distributed around a median circumference. The screws are screwed into the counter-ring, creating a gap to the intermediate ring, and bracing them against the adjusting ring. This known machine element solution therefore uses three ring components that are permanently connected to each other in series via membrane parts with thin wall sections. Several adjusting bolts or stud bolts that are distributed evenly around the outer circumference of the ring nut serve as adjustment devices.
In a comparable, known solution, as described in DE 10 2004 003 183 A1, an annular groove that extends from the inner circumference surface is provided for the subdivision into a ring component that acts as adjusting ring and into a ring component that acts as counter-ring. Both are provided with the same internal thread, in which again a connection via a membrane component in form of a thin wall section is provided. As before, several adjusting bolts distributed evenly around the outer circumference serve as the adjusting device.
The manufacturing process of such single-piece solutions with membrane components is relatively elaborate since the materials that are suitable, such as stainless steel or titanium, are difficult to machine, which is not conducive to an economical production of the membrane components.
In order to avoid the disadvantages in connection with the single-piece solutions, the document DE 199 12 068 B4 describes a machine element of the two-part kind as stated at the outset. Since in this instance the ring components that form the locking ring and the adjusting ring are produced as discrete components, the manufacture of a soft membrane is no longer necessary, which alleviates the associated production problems and limitations regarding choice of materials. Nevertheless, a significant disadvantage lies in the large number of individual components that are included in this known solution as functional components.
Although the clamping screws of the adjusting device are omitted in this solution, the ring component that acts as adjusting ring and the ring component that acts as locking ring are coupled together in such a way that they form a positively locked unit. The ring components then remain locked to each other in terms of orientation and pitch of the threads. To achieve this, connecting bolts are provided that pass through the ring component that acts as locking ring. The bolt shafts are pressed into blind holes in the component that acts as adjusting ring. Their bolt heads limit the relative axial movements between the ring components to a maximum distance. Added to the increased number of components is the production cost required to make the press fits for the bolts.
A further disadvantage is that an increased number of bore holes must be machined into the ring component that forms the locking ring. To limit weakening of the structure, the known solution has, in addition to the three bore holes for the connecting bolts, only three bore holes for a clamping screw each. This arrangement leads to an unfavorable distribution of the clamping force. Despite limiting the clamping screws to a lower number, the structural rigidity of the component that acts as locking ring is compromised. As shown in that document of the known solution, three further threaded bore holes are provided for each adjusting screw that serve as an assembly aid, which arrangement of bore holes increases the number through holes to nine. The production effort for the known solution is additionally increased by coil springs, which retain the ring components, coupled by the connecting bolts, frictionally locked at an axial maximum distance.